1. Field of the Invention
The present invention concerns hydraulically operated actuators which use multiple metal-to-metal static seals and, more particularly, such actuators employed as external operators for subsea valves.
2. Description of the Prior Art
Conventional elastomer type seals have been used heretofore on hydraulically operated type actuators to prevent contamination of the power fluid in subsea and/or well environments. Those environments are corrosive and degrading to most elastomeric (resilient) materials and , consequently, such seals are of questionable reliability. The metal-to-metal static seals of the present invention have greater reliability than the elastomer seals. The metals (alloys) which form the metallic static seals are much less susceptible to deterioration and failure from chemical attack and high temperatures than elastomer compounds currently being used for actuator seals. Further, the actuator-safety valve design of the present invention is more reliable than known conventional actuator safety valve designs and achieves full through-bore capability required for wire line and pump-down tool work. Also, metal-to-metal seals are not contained in such conventional designs. In addition, conventional downhole safety valves are subject to seal leakage due to transfer of loads through the hydraulic components whereas in the present invention, axial loads in the tubing string do not affect operation of the hydraulic system.